The Mayor of Toronto weighs more than 300 pounds and when I ran with him around the track by his home on Sunday, I was scared for his health.

Rob Ford’s face was red and he was sweating, even though it was cold out and we were charging through snow. He was by himself, with no water, and he was breathing hard and finding it difficult to talk. Don’t get me wrong, the effort he was employing was noble. With the hood of his cotton sweatshirt popped over his head, Ford was swinging his arms mightily and definitely working hard to complete his 20 laps. It’s just that there’s a line between setting a goal and sticking to it, and it can be dangerous when a sense of determination clouds common sense.

“We know the benefits of exercise outweigh the risks, but it’s important not to do too much too soon, and not just for the heart, but for the entire body,” says Dr. Mark Haykowsky, a marathon runner and professor with the faculty of rehabilitation at the University of Alberta. Haykowsky specializes in working with heart transplant recipients and is an expert at designing exercise routines for those, like Mayor Ford, who have cardiovascular risk factors. During our run, the Mayor didn’t appear dizzy or complain of chest pains — on the contrary, we talked about the day’s big football games — but his laboured breathing and colouring were worrisome. When I asked him if he wanted some water, he said he was OK.

“For moderate exercise, you should be able to talk; you should rest for a moment if you feel a shortness of breath,” says Haykowsky, who recommends all runners, but especially those over 45, take the PAR-Q questionnaire on the Canadian Society for Exercise Physiology website before beginning any training program. “The nice thing about being very de-conditioned is that you’ll improve your fitness quickly, but you need to build your base and run safely if you want to remain healthy for the long haul.”

Mayor Ford jogged for a bit at the start of our run — when I joined him he had already power-walked 12 laps on his way towards his 20 — and then very quickly settled into a sort of hard-stomping stride. He wasn’t lifting his feet very high and had his head down and his arms out, driving ahead like a freight train.

“It’s like running in molasses — you feel like you’re not going anywhere,” says Pam MacCormack, 62, from Gloucester, Ont., who began running at 57, when she weighed 320 pounds. “Your legs are like tree stumps and there’s a heaviness in your chest. When you’re just starting out as a runner, there’s a mental burden as well as the physical weight.”

MacCormack, a retired customs officer, describes surviving years of abuse from people insensitive to her weight. “I took a lot of hits, people laughing at me, telling jokes. ‘Pam MacCormack, you think she’s ever heard of a salad?’ Or someone goes: ‘Are we finished? No, Pam hasn’t started to sing.’ ”

MacCormack sought refuge from the abuse through overeating, and she talks about medicating herself with quick sugar or carbohydrate highs. “You build up a barrier to protect yourself against the cruelty for awhile, but it’s a downward spiral. And the food rush I was getting inevitably would lead to a crash.”

In 2007, MacCormack zipped up her parka and put on her snow boots and attended her first walking clinic at the Running Room. She was dressed completely wrong, but she liked the feeling and remains in the clinics — off and on, and through various injuries and weight fluctuations — today. At last count, she had lost 150 pounds.

“Running is an amazing feeling, a rush I’ve never felt before. It’s like I’ve found a new medication,” she says. “It’s such a hit.”

Mayor Ford is still early in his exercise program, but his tenacity was a site to behold. In politics, the Mayor is nothing if not stubborn, and that same stubbornness appears to be leading him towards his goal. Initially, he plans to try to lose 50 pounds by June, but he also says he wants to lose 100 pounds in a year. He’s already lost 10 pounds in a week with his training, and I asked him if he had any advice for other people battling obesity and wanting to lose weight.

“Keep it up,” he said on Sunday. Later, I heard that he walked eight extra laps.